strcpy 断言错误 C++

Question

我是一名学生，刚刚学习 c++，所以我确信有更有效的方法可以做到这一点；话虽如此，我真的很感激能帮助我弄清楚我的程序崩溃的原因。我已将其范围缩小为 strcpy 函数，该函数会使所有内容崩溃并破坏它，我已将其注释掉并标记。我显然在程序中多次使用了类似参数的 strcpy 函数，所以我不明白为什么那个特定的函数会崩溃。我已经尝试了我能想到的一切，并且非常感谢您的帮助。到目前为止，我已经注释掉了很多内容，因此它应该使用名为“bookdb”的正确文本文件运行，我的文本文件中目前有这个

Active Learning Approach,Randal Albert,9780763757236,1,650,1,<br>
Technical Communications,John Lannon,9780321899972,2,724,0,

要查看错误，您必须取消注释 strcpy(bookArray[num_books].author_name, temp_authorName);

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <iomanip>
#include <fstream>
#include <cstring>

enum Genres {HORROR=1, SCIFI, COMEDY, DRAMA, ACTION};


struct Book
{
    char title[100];
    char author_name[50];
    char isbn[14];
    Genres genre;
    int num_pages;
    bool paperback;
};

//Function Declarations
unsigned short ReadBooks(Book * bookArray, unsigned short & num_books);
void DisplayBooks(Book * bookArray, unsigned short num_books);
void ResizeArrays(Book * bookArray, unsigned short num_books);

int main ()
{
    unsigned short num_books = 0;
    Book * bookArray = new Book();

    num_books = ReadBooks(bookArray, num_books);

}//End Main

unsigned short ReadBooks(Book * bookArray, unsigned short & num_books)
{
    ifstream readBooks("bookdb.txt");
    char temp_title[100] = "0";
    char temp_authorName[100] = "0";
    char temp_isbn[14] = "0";

    char temp_genre[50] = "0";
    char temp_numPages[50] = "0";
    char temp_paperback[50] = "0";

    int genreNumber = 0,
        numPages = 0,
        paperback = 0;

    if (readBooks.is_open() )
    {
        cout << "The file was successfully opened\n" << endl;

        readBooks.getline(temp_title, 100, ',');//Reads into temp cstring
        strcpy(bookArray[num_books].title, temp_title); //copies to dynamic cstring
        //cout << bookArray[num_books].title << endl; //displays part of structure to make sure it worked!!

        readBooks.getline(temp_authorName, 100, ',');
        strcpy(bookArray[num_books].author_name, temp_authorName); 
        //cout << bookArray[num_books].author_name << endl; 

        readBooks.getline(temp_isbn, 14, ',');
        strcpy(bookArray[num_books].isbn, temp_isbn); 
        //cout << bookArray[num_books].isbn << endl;

        readBooks.getline(temp_genre, 50, ',');//Get the genre as a char
        genreNumber = atoi(temp_genre);//converts char to an int
        bookArray[num_books].genre = static_cast <Genres> (genreNumber);//converts int to ENUM
        //cout << bookArray[num_books].genre << endl;//Displays ENUM to make sure it worked!!

        readBooks.getline(temp_numPages, 50, ',');
        numPages = atoi(temp_numPages); //converts char to an int
        bookArray[num_books].num_pages = numPages; //assigns int to structure
        //cout << bookArray[num_books].num_pages << endl; //Displays part of structure to make sure to works!!

        readBooks.getline(temp_paperback, 50, ',');
        paperback = atoi(temp_paperback); //converts char to an int
        bookArray[num_books].paperback = static_cast <bool> (paperback);
        //cout << bookArray[num_books].paperback << endl;
        num_books++;

        //DisplayBooks(bookArray, num_books);
        ResizeArrays(bookArray, num_books);
        cout << "The number of books is: " << num_books << endl;

        //while (!readBooks.eof() )
        //{

        readBooks.getline(temp_title, 100, ',');//Reads into temp cstring
        strcpy(bookArray[num_books].title, temp_title); //copies to dynamic cstring
        cout << bookArray[num_books].title << endl; //displays part of structure to make sure it worked!!

        readBooks.getline(temp_authorName, 100, ',');
        cout << temp_authorName << endl; 
        //strcpy(bookArray[num_books].author_name, "0");
        ///THIS BREAKS MY CODE////strcpy(bookArray[num_books].author_name, temp_authorName); 
        //cout << bookArray[num_books].author_name << endl; 

        readBooks.getline(temp_isbn, 14, ',');
        //strcpy(bookArray[num_books].isbn, temp_isbn); 
        //cout << bookArray[num_books].isbn << endl;

        readBooks.getline(temp_genre, 50, ',');//Get the genre as a char
        //genreNumber = atoi(temp_genre);//converts char to an int
        //bookArray[num_books].genre = static_cast <Genres> (genreNumber);//converts int to ENUM
        //cout << bookArray[num_books].genre << endl;//Displays ENUM to make sure it worked!!

        readBooks.getline(temp_numPages, 1000, ',');
        //numPages = atoi(temp_numPages); //converts char to an int
        //bookArray[num_books].num_pages = numPages; //assigns int to structure
        //cout << bookArray[num_books].num_pages << endl; //Displays part of structure to make sure to works!!

        readBooks.getline(temp_paperback, 50, ',');
        //paperback = atoi(temp_paperback); //converts char to an int
        //bookArray[num_books].paperback = static_cast <bool> (paperback);
        //cout << bookArray[num_books].paperback << endl;*/

        num_books++;

        //ResizeArrays(bookArray, num_books);
        //}//End while

        readBooks.close();
    }//End if
    else
    {
        cout << "There was not an existing book file, so one will be created"  << endl;
    }//End else

    return 0;
}//End ReadBooks

void DisplayBooks(Book * bookArray, unsigned short num_books)
{
    for (unsigned short i = 0; i < num_books; i++)
    {
        cout << setw(30) << left << bookArray[i].title << left << setw(20) << bookArray[i].author_name << left << setw(15) << bookArray[i].isbn
             << left << setw(3) << bookArray[i].genre  << left<< setw(6) << bookArray[i].num_pages << left << setw(4) << bookArray[i].paperback << endl;
    }//End For
}//ENd Display Function

void ResizeArrays(Book * bookArray, unsigned short num_books)
{
    Book * temp_bookArray = new Book[num_books + 1];


    for (int i = 0; i < num_books; i++)
    {
        strcpy(temp_bookArray[i].title, bookArray[i].title);
        //cout << temp_bookArray[i].title << endl; //For Debugging

        strcpy(temp_bookArray[i].author_name, bookArray[i].author_name);
        //cout << temp_bookArray[i].author_name << endl; //for Debugging

        strcpy(temp_bookArray[i].isbn, bookArray[i].isbn);
        //cout << temp_bookArray[i].isbn << endl;//for debugging

        temp_bookArray[i].genre = bookArray[i].genre;
        //cout << temp_bookArray[i].genre << endl;//for debugging

        temp_bookArray[i].num_pages = bookArray[i].num_pages;
        //cout << temp_bookArray[i].num_pages << endl;// for debugging

        temp_bookArray[i].paperback = bookArray[i].paperback; 
        //cout << temp_bookArray[i].paperback << endl; //for debugging


    }//End for

    delete [] bookArray;

    bookArray = temp_bookArray; 

    DisplayBooks(bookArray, num_books); //debugging to make sure bookArray is reassigned


}//End Resize Function

Answer 1

strlen 获取所有没有 '\0' 的元素，所以如果你有 str = "1234"; str 长度为 5,(1234 + '\0) 但返回 4.Strcpy 取所有 5 个元素 + '\0' 。

Answer 2

ResizeArrays 存在问题：

• 它为数组分配新内存，但不会将该新数组返回给调用函数，以便调整指向新数组位置的指针。
• 可能需要调整大小、旧大小和新大小，您只能复制这些元素中的最小值。

为了解决这个问题，您可以执行以下操作：

Book* ResizeArrays(Book * bookArray, unsigned short num_books)
{ 
    ....
    return bookArray;
}

那么就这样使用函数

bookArray = ResizeArrays(bookArray, num_books);

但是，当您使用数组删除时，对于您的第一次分配，您也需要在 main() 中使用数组分配，

Book * bookArray = new Book[1];

虽然它只分配一本书，但它应该作为一个数组来完成，因此它与 ResizeArrays 中使用的 delete [] 兼容。

我认为这是一个学习练习。在正常使用 C++ 时，您不会使用裸 new 和 delete 运算符。您可以简单地使用 std::vector 或类似的，或者创建一个管理内存的对象，分别在构造函数和析构函数中使用 new 和 delete。

Answer 3

我看到的问题：

问题 1

没有足够的空间来正确保存 ISBN。输入文件中 ISBN 的长度为 14 个字符。要将它们保存在以空字符结尾的字符串中，您需要有一个可以容纳 15 个或更多字符的数组。

结果，一行

    readBooks.getline(temp_isbn, 14, ',');

将在 13 个字符后停止读取，因为它必须使用第 14 个字符来存储 '\0'。

问题 2

这条线看起来不对。

    readBooks.getline(temp_numPages, 1000, ',');

我怀疑这是一个错字，你的意思是

    readBooks.getline(temp_numPages, 50, ',');

问题 3

ResizeArray 中的内存处理存在问题。

void ResizeArrays(Book * bookArray, unsigned short num_books)
{
    Book * temp_bookArray = new Book[num_books + 1];

    // Here, you are deleting the memory that was allocated in `main`.
    // bookArray in the calling function now points to memory that has been
    // deleted here.
    delete [] bookArray;

    // Here, you are changing the value of bookArray but only
    // locally in this function. This assignment doesn't
    // change the value of bookArray in the calling function.
    bookArray = temp_bookArray; 

    DisplayBooks(bookArray, num_books); //debugging to make sure bookArray is reassigned


}//End Resize Function

如果您将ResizeArray 更改为：

void ResizeArrays(Book*& bookArray, unsigned short num_books)

一切都会好起来的。

问题 4

我看到您已经注释掉了ReadBooks 中的while 循环。如果您决定恢复该循环，则必须在每次循环运行时调整 bookArray 的大小。

建议 使用std::vector<Book*> 来保存书籍会更容易，而不是为Books 的数组分配内存。